DOE OSTI2020
Ca2(TlPb)3 crystallizes in the orthorhombic Pmmm space group. The structure is three-dimensional. Ca is bonded to six Tl and six Pb atoms to form CaTl6Pb6 cuboctahedra that share corners with twelve equivalent CaTl6Pb6 cuboctahedra, edges with twelve TlCa4Tl4Pb4 cuboctahedra, faces with six equivalent CaTl6Pb6 cuboctahedra, and faces with six TlCa4Tl4Pb4 cuboctahedra. There are a spread of Ca–Tl bond distances ranging from 3.47–3.49 Å. There are four shorter (3.47 Å) and two longer (3.49 Å) Ca–Pb bond lengths. There are three inequivalent Tl sites. In the first Tl site, Tl is bonded to four equivalent Ca, four equivalent Tl, and four equivalent Pb atoms to form distorted TlCa4Tl4Pb4 cuboctahedra that share corners with four equivalent TlCa4Tl4Pb4 cuboctahedra, edges with eight equivalent CaTl6Pb6 cuboctahedra, edges with eight equivalent TlCa4Pb8 cuboctahedra, faces with four equivalent CaTl6Pb6 cuboctahedra, and faces with eight TlCa4Tl4Pb4 cuboctahedra. All Tl–Tl bond lengths are 3.47 Å. All Tl–Pb bond lengths are 3.47 Å. In the second Tl site, Tl is bonded to four equivalent Ca and eight Pb atoms to form TlCa4Pb8 cuboctahedra that share corners with twelve TlCa4Pb8 cuboctahedra, edges with eight equivalent CaTl6Pb6 cuboctahedra, edges with eight equivalent TlCa4Tl4Pb4 cuboctahedra, faces with four equivalent CaTl6Pb6 cuboctahedra, and faces with six TlCa4Pb8 cuboctahedra. There are four shorter (3.47 Å) and four longer (3.50 Å) Tl–Pb bond lengths. In the third Tl site, Tl is bonded to four equivalent Ca, four equivalent Tl, and four equivalent Pb atoms to form distorted TlCa4Tl4Pb4 cuboctahedra that share corners with twelve TlCa4Pb8 cuboctahedra, edges with eight equivalent CaTl6Pb6 cuboctahedra, faces with four equivalent CaTl6Pb6 cuboctahedra, and faces with ten TlCa4Tl4Pb4 cuboctahedra. All Tl–Pb bond lengths are 3.46 Å. There are two inequivalent Pb sites. In the first Pb site, Pb is bonded in a 12-coordinate geometry to four equivalent Ca and six Tl atoms. In the second Pb site, Pb is bonded in a 12-coordinate geometry to four equivalent Ca and four equivalent Tl atoms.